| PCE | Q. Xiong |
| Internet-Draft | ZTE Corporation |
| Intended status: Standards Track | June 1, 2020 |
| Expires: December 3, 2020 |
LSP Object Flag Extension of Stateful PCE
draft-xiong-pce-lsp-flag-02
RFC8231 describes a set of extensions to PCEP to enable stateful control of MPLS-TE and GMPLS Label Switched Paths(LSPs) via PCEP. One of the extensions is the LSP object which includes a Flag field and the length is 12 bits. However, 11 bits of the Flag field has been assigned in RFC8231, RFC8281 and RFC8623 respectively.
This document proposes to define a new LSP-EXTENDED-FLAG TLV for LSP object to extend the length of the flags.
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on December 3, 2020.
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[RFC5440] describes the Path Computation Element Protocol (PCEP) which is used between a Path Computation Element (PCE) and a Path Computation Client (PCC) (or other PCE) to enable computation of Multi-protocol Label Switching (MPLS) for Traffic Engineering Label Switched Path (TE LSP).
PCEP Extensions for the Stateful PCE Model [RFC8231] describes a set of extensions to PCEP to enable active control of MPLS-TE and Generalized MPLS (GMPLS) tunnels. One of the extensions is the LSP object which contains a flag field indicating to a PCE that the LSP State Synchronization is in progress.
As defined in [RFC8231], the length of the flag field is 12 bits and the value from bit 5 to bit 11 is used for operational, administrative, remove, synchronize and delegate respectively. The bit value 4 is assigned in [RFC8281] for create. The bits from 1 to 3 is assigned in [RFC8623] for ERO-compression, fragmentation and P2MP respectively. Almost all bits of the Flag field has been assigned in RFC8231, RFC8281 and RFC8623 respectively. It is required to extend the length of the flag field for other cases.
This document proposes to define a new LSP-EXTENDED-FLAG TLV for LSP object to extend the length of the flag.
The terminology is defined as [RFC5440] and [RFC8231].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
The LSP Object is defined in Section 7.3 of [RFC8231]. This document proposes to define a new LSP-EXTENDED-FLAG TLV for LSP Object to extend the length of the flag.
The format of the LSP-EXTENDED-FLAG TLV is as shown in the Figure 1.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// LSP Extended Flags //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: LSP-EXTENDED-FLAG TLV Format
Type (16 bits): the value is TBD1 by IANA.
Length (16 bits): multiple of 4 octets.
LSP Extended Flags: this contains an array of units of 32-bit flags numbered from the most significant as bit zero, where each bit represents one LSP capability or state.
The LSP Extended Flags field is an array of units of 32 flags and being used starting from the least significant bit. Any bit being assigned indicates a special LSP capability or state when the bit is set to 0. No bits are defined in this document and the bits of the LSP Extended Flags field MAY be assigned for future uses and IANA will manage the space of the LSP Extended Flags. Unassigned bits are reserved and SHOULD be set to zero on transmission and MUST be ignored on receipt.
The LSP-EXTENDED-FLAG TLV MUST be included in the LSP Object when the bits of the extended flag field need to be used. If the TLV is missing, the PCE will generate an error with Error-type=6 (Mandatory Object missing) and error-value TBD2 (LSP-EXTENDED-FLAG TLV missing) and close the session.
The LSP-EXTENDED-FLAG TLV defined in this document does not introduce any interoperability issues.
A router not supporting the LSP-EXTENDED-FLAG TLV will just silently ignore the TLV as specified in section 3.2.
The LSP-EXTENDED-FLAG TLV MUST be defined as mandatory when a router supporting the LSP Object and needs to use the extended flag field.
IANA has assigned a registry for TLVs carried in the LSP Object defined in [RFC8231]. IANA is requested to make allocations for the LSP-EXTENDED-FLAG TLV carried within LSP Object from the "PCEP TLV Type Indicators" subregistry of the "Path Computation Element Protocol (PCEP) Numbers" registry, as follows:
| Value | Description | Reference |
|---|---|---|
| TBD1 | LSP-EXTENDED-FLAG TLV | [This document] |
IANA is requested to create a new subregistry, named "LSP Extended Flags Field", from the "Path Computation Element Protocol (PCEP) Numbers" registry to manage the LSP Extended Flags field of the LSP-EXTENDED-FLAG TLV. New values MUST request to be assigned by Standards Action [RFC8126] and IANA will manage the space of the bit flags numbering them in the usual IETF notation starting at zero and continuing at least through 31. Each bit should be tracked with the following qualities:
Bit number (counting from bit 0 as the most significant bit)
Capability description
Defining RFC
IANA is requested to register the following error types and error values within the "PCEP-ERROR Object Error Types and Values" subregistry of the "Path Computation Element Protocol (PCEP) Numbers" registry:
| Error-Type | Meaning |
|---|---|
| 6 | Mandatory Object missing |
| Error-value | |
| TBD2: LSP-EXTENDED-FLAG TLV missing |
For LSP Object procssing security considerations, see [RFC8231].
No additional security issues are raised in this document beyond those that exist in the referenced documents.
Authors would like to thank the comments and suggestions from Dhruv Dhody and Farrel Adrian.